1. Field of the Invention
The present invention relates to a surface mount antenna including a radiation electrode disposed on a dielectric substrate, an antenna device including such an antenna, and a communication device
2. Description of the Related Art
Recently, great attention has been paid to a multi-band antenna in which radio communication can be carried out in a plurality of frequency bands by use of one antenna. For example, a radiation electrode which carries out antenna-operation has plural resonance modes having different resonance frequencies. Thus, multi-band antennas are used to perform radio communication in plural frequency bands by utilization of the plurality of resonance modes of the radiation electrode (see Japanese Unexamined Patent Application Publication No. 2002-26624 (Patent Document 1), European Patent Application Publication No. EP 0938158 A2 Specification (Patent Document 2), International Publication No. WO99/22420 Pamphlet (Patent Document 3), and Japanese Unexamined Patent Application Publication No. 2002-158529 Patent Document 4).
Generally, for the multi-band antennas using plural resonance modes of a radiation electrode, the resonance in the fundamental mode and higher-order modes is used. That is, the frequency of the fundamental mode resonance is lowest in the plural resonance modes of the radiation electrode, and the frequencies of the higher-order mode resonance are higher compared to the frequency of the fundamental mode resonance. Thus, the radiation electrode is set as follows: the fundamental mode resonance of the radiation electrode is carried out in the lower frequency band of plural frequency bands set for radio communication, and the higher-order mode resonance of the radiation electrode is carried out in the higher frequency band of the plural frequency bands set for radio communication.
However, for example, for small-sized antennas such as surface mount antennas, it is difficult to independently control the fundamental mode resonance of the radiation electrode and the higher-order mode. For example, there are some cases in which the fundamental mode resonance can be satisfactorily carried out, but the higher-order mode resonance is insufficient. Thus, it is difficult to form the radiation electrode so that both of the fundamental mode resonance and the higher-order mode resonance can be satisfactorily carried out.